Oleic acid is characterized as?

• A. 18 carbons, long chain
• B. 12 carbon atoms, medium chain fatty acid
• C. 4 carbons, short chain fatty acid
• D. 20 carbons, very long chain fatty acid

Answer: (A)

Fatty acids are categorized by how many carbon atoms they contain. Short-chain is roughly up to 6 carbons, medium-chain up to about 12, and long-chain is more than about 12 carbons. Oleic acid has 18 carbon atoms, so it clearly falls into the long-chain fatty acid group. It’s also a monounsaturated fatty acid, but the key point here is the carbon count that defines long-chain status. The other numbers don’t fit: 12 carbons is medium-chain, 4 carbons is short-chain, and while 20 carbons would be long-chain, oleic acid specifically has 18 carbons.